Lakehead University Knowledge Commons

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Assessing head impact reduction through under-mat systems: A fall simulation study of Ippon-Seoi-Nage and Osoto-Gari in Judoka
(2026) Henson, Kylee; Zerpa, Carlos; Prysucha, Eryk; Sanzo, Paolo; Liu, Meilan
Concussion rates are increasing in the sport of Judo. Most research on prevention focuses on how athletes respond to throws or the types of protective equipment they use to reduce impacts to the head and body. There is, however, a lack of research on the effectiveness of Judo mats in minimizing the risk of concussion during falls. In response to this research need, the proposed study explored the material properties of Judo under-mat systems by measuring their energy absorption through static testing. It also examined how different under-mat systems mitigate impact force, reduce acceleration, and lower the risk of head injuries during simulated dynamic falls in Judoka. Specifically, the study simulated scenarios when an athlete lands on the mat after being thrown with the Osoto-Gari technique and when an athlete hits the head on the mat while being thrown with the Ippon-Seoi-Nage technique. Four under-mat systems commonly seen in Judo training centers in Ontario were examined: a Judo mat with no under-mat, a pool noodle under-mat, a hockey puck under-mat, and an insulation under-mat system. Descriptive statistics, including means and standard deviations, were computed, and inferential statistical analyses were performed utilizing mixed factorial ANOVAs to address the purpose of this study. The static testing results showed that the pool noodles and hockey pucks absorbed less energy than the baseline under-mat system, but they may provide more cushioning for athletes during falls. The dynamic simulations and human participant testing revealed that the pool noodle and hockey puck under-mat systems seemed to better mitigate the risk of concussion based on measures of force, linear and angular acceleration during the simulation of Osoto-Gari and Ippon-Seoi-Nage Judo techniques. The outcome of this study provides an avenue to assess the effectiveness of Judo under-mat systems in training centers to prevent concussion risk.
A dual-purpose optimal mono-stable nonlinear energy sink with a grounded electromagnetic energy harvester
(2026) Jin, Youzuo; Liu, Kefu; Wang, Wilson; Deng, Jian
The motivation of this dissertation is to develop an optimal mono-stable nonlinear energy sink (MSNES) capable of achieving simultaneous vibration suppression (VS) and energy harvesting (EH) over a wide frequency band. Conventional nonlinear energy sinks often suffer from limited tunability for stability variation and inability of harvesting energy, motivating the development of a systematic and reconfigurable design. Accordingly, this dissertation pursues three main objectives: (1) to develop a tunable nonlinear energy sink (TNES); (2) to establish a design methodology for tuning the TNES into an optimal MSNES; and (3) to evaluate the VS and EH performance of the optimal MSNES through numerical simulations and experimental validation. For the first objective, a TNES is developed using an S-shaped pinned–pinned beam carrying a pair of oscillating magnets at its midpoint. These magnets interact with four tuning magnets mounted on the primary structure to form a magnetically tunable nonlinear spring. As the oscillating magnets move, they pass through a pair of coils rigidly fixed to the base, forming dual electromagnetic energy harvesters (EMEHs). Because the coils are mechanically grounded and connected in series to a resistive load, the EMEHs function as a grounded electromagnetic damper while enabling large-amplitude translational motion. For the second objective, an equivalent stiffness method is employed to characterize the essentially nonlinear stiffness of a target nonlinear energy sink. A numerical optimization procedure is then developed to determine the optimal tuning parameters that allow the TNES to emulate the desired MSNES behavior. For the third objective, extensive numerical simulations are conducted to assess the transient VS and EH performance of the optimal MSNES, followed by experimental validation. The trade-off between vibration suppression and energy harvesting, as well as the effects of primary system detuning, are examined. The main contributions of this dissertation are fourfold. First, the proposed TNES architecture enables convenient reconfiguration among mono-stable, bi-stable, and tri-stable states. Second, the grounded electromagnetic energy harvester facilitates large-amplitude translational motion and efficient energy extraction. Third, a systematic design framework is established to obtain an optimal MSNES that closely emulates an ideal nonlinear energy sink. Finally, numerical and experimental results show strong agreement, confirming the effectiveness of the proposed MSNES in delivering broadband vibration suppression and energy harvesting.
Being Black in Canada: Anti-Black racism and the lived experiences of Canadian Black men
(2026) Charles, Sherelle; Agbo, Seth; Hoeschmann, Michael
Anti-Black racism (ABR) remains a persistent social justice issue with historical roots extending into contemporary times in the North American context. Throughout history, it has been employed as an oppressive tool, advancing in nuanced forms that permeate foundational institutions and societal perceptions, effectively perpetuating the oppression of Black individuals. This phenomenon establishes societal barriers, limiting opportunities and fostering unfavorable outcomes across education, socio-economic status, criminal justice, and healthcare for Black communities. The objective of this research is to comprehend and illuminate the experiences of Black Canadian men regarding ABR. This study utilizes a qualitative interpretative phenomenological method, employing semi-structured one-on-one interviews conducted over Zoom with eight participants selected from the researcher’s pool of Black male family and friends. The exploration yielded insights into systemic discrimination and racism, everyday racism, implicit biases, systemic barriers, and the negative impacts of ABR on physical and mental well-being, as well as existing anti-ABR initiatives. The findings of the present study indicate that there are significant and disproportionate challenges faced by Black men in Canada due to ABR, including systemic barriers in employment, societal hindrances to holistic progress, and the need for heightened awareness of racial identity. Despite these obstacles, participants demonstrated resilience, emphasizing the critical importance of Black representation and leadership, and underscoring the urgent need for equitable practices and increased visibility to support Black men as valued members of Canadian society. The research underscores urgent implications for policymakers, organizations, and the Black community. Structural reforms across education, leadership, and hiring practices are needed to move beyond performative commitments to anti-racism. Culturally affirming programs, mentorship, and accessible resources can strengthen community resilience and agency, particularly for Black men. Targeted legislation, accountability mechanisms, and sustained investment in Black-led initiatives are essential for addressing systemic inequities, fostering inclusivity, and promoting equity at both institutional and national levels.
Exploring the experiences of Indigenous patients accessing naturopathic medicine in Thunder Bay Ontario
(2026) Carfagnini, Jessica; Moeller, Helle; Levkoe, Charles; Manitowabi, Darrel
Health inequities for Indigenous Peoples across Turtle Island have been well documented, but the role of naturopathic doctors in contributing to Indigenous-led health-care initiatives remains understudied. Very little research exists documenting the experiences of Indigenous individuals with naturopathic medicine. This exploratory qualitative research study contributes to addressing this gap by exploring the experiences of twelve Indigenous individuals who have accessed care from licensed naturopathic doctors in Thunder Bay, Ontario. Couched in discussions about the impact of colonization and ongoing colonialism on their health and health care, participants expressed that the philosophy of naturopathic medicine aligns with Indigenous concepts of health and healing being holistic, collaborative, patient-centred and offering natural treatment options. In addition, participants experienced naturopathic doctors as trustworthy well-educated health-care providers who listened. Cultural appropriation and the need for NDs to become more culturally competent as health-care practitioners are also explored. Barriers to accessing naturopathic care included the cost of appointments and prescribed substances, lack of awareness and misconceptions about naturopathic medicine, and geographical limitations. Indigenous patients accessing naturopathic medicine in Thunder Bay articulated that it has a key role to play in the health care they desire for themselves, their families and communities. Future research projects can query whether this finding holds true in other regions, what the experiences are of Indigenous Peoples who have not accessed naturopathic medicine, and can explore the role of naturopathic medicine in Indigenous-led health care.
Development of a pendulum-based device to harvest energy from large amplitude, low-frequency oscillations
(2026) Banerjee, Gairik; Liu, Kefu
The rapid growth of the Internet of Things (IoT), wearable electronics, and remote sensing technologies has created strong demand for sustainable, self-powered devices. Vibration energy harvesting aims to meet this need by converting ambient mechanical energy into electricity. However, traditional spring–mass harvesters are limited by static deformation (vertical type), friction losses (horizontal type), restricted motion range, and narrow bandwidths, while conventional pendulum harvesters typically require large motion clearance, reducing compactness and power density. To address these challenges, this work develops a compact pendulum-based electromagnetic energy harvester (EMEH) integrating spiral torsional springs and a dual Halbach magnet array. The spiral springs serve as motion limiters, maintain axial compactness, and allow large angular deflections, whereas the Halbach array produces intensified unidirectional magnetic fields to enhance electromagnetic coupling. A lumped-parameter model is formulated to describe the coupled electromechanical dynamics. Spiral springs are designed and 3D-printed in PLA, and their stiffness is characterized through finite-element analysis, static torque–angle testing, and natural- frequency measurements. Two coil arrangements for the EMEH are examined, and their electromagnetic transduction factors are obtained from COMSOL magnetic-flux simulations. Using the computed transduction factors and the dynamic model, free-voltage responses across various load resistances are generated via numerical simulation and compared with experimental measurements. Results show that the second coil configuration yields closer agreement between simulated and measured responses, indicating stronger electromagnetic coupling and improved model fidelity. The energy harvesting performance of the proposed EMEH is further examined through systematic free-response and base-excitation analyses across five mechanical configurations, with different stiffnesses and mounting strategies. Performance metrics including harvested electrical energy, peak power, average power, and energy conversion efficiency are evaluated over a wide range of load resistances and excitation amplitudes. Harmonic and swept-frequency numerical simulations are employed to investigate the system response under sinusoidal base excitation, revealing the trade-offs between stiffness-induced frequency tuning, motion regulation, bandwidth variation, and electrical power output.